linux-kernel - Re: [PATCH -V7 21/26] richacl: xattr mapping functions

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Message-ID: <20111020091434.GC5444@fieldses.org>
Date:	Thu, 20 Oct 2011 05:14:34 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	agruen@...nel.org, akpm@...ux-foundation.org,
	viro@...iv.linux.org.uk, dhowells@...hat.com,
	linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -V7 21/26] richacl: xattr mapping functions

On Thu, Oct 20, 2011 at 02:00:02PM +0530, Aneesh Kumar K.V wrote:
> On Wed, 19 Oct 2011 18:20:21 -0400, "J. Bruce Fields" <bfields@...ldses.org> wrote:
> > On Tue, Oct 18, 2011 at 09:02:56PM +0530, Aneesh Kumar K.V wrote:
> > > +#define RICHACL_XATTR "system.richacl"
> > > +
> > > +struct richace_xattr {
> > > +	__le16		e_type;
> > > +	__le16		e_flags;
> > > +	__le32		e_mask;
> > > +	__le32		e_id;
> > > +	char		e_who[0];
> > > +};
> > 
> > Does it really make sense to use a string here just to pick between the
> > three choices OWNER@, GROUP@, and EVERYONE@?  Why not just another small
> > integer?  Is the goal to expand this somehow eventually?
> 
> I guess Andreas wanted the disk layout to be able to store user@...ain
> format if needed.

Is that likely?  For that to be useful, tasks would need to be able to
run as user@...ain strings.  And we'd probably want owners and groups to
also be user@...ain strings.

The container people seem to eventually want to add some kind of
namespace identifier everywhere:

	http://marc.info/?l=linux-kernel&m=131836778427871&w=2

in which case I guess we'd likely end up with (uid, user namespace id)
instead of user@...ain?

I suppose the variable-length string field could store that too.

I don't hate the idea, it would make life easier for the NFS server.

--b.

> That should make the layout flexible enough so that
> we won't have to add another xattr later.
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